


a favor's a favor

by supernormal



Series: Sengen gentle dom [9]
Category: Dr. STONE (Anime), Dr. STONE (Manga)
Genre: Blow Jobs, Body Worship, Exhibitionism, Getting Together, Humiliation, M/M, Maybe - Freeform, Modern AU, Plot What Plot/Porn Without Plot, Praise Kink, Top Asagiri Gen, a lot of internal monologue, bottom ishigami senku, has accompanying art in end note, micro bikini
Language: English
Status: Completed
Published: 2020-11-16
Updated: 2020-11-16
Packaged: 2021-03-10 01:02:02
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,250
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27585155
Author URL: https://archiveofourown.org/users/supernormal/pseuds/supernormal
Summary: Gen asks Senku to model something for him.
Relationships: Asagiri Gen/Ishigami Senkuu
Series: Sengen gentle dom [9]
Series URL: https://archiveofourown.org/series/1726681
Comments: 1
Kudos: 78





	a favor's a favor

**Author's Note:**

> big fan of writing fics with absolutely ridiculous premises

Senku knocked on the door. He took another glance at the number. _401, right? Right._ He tapped his foot somewhat impatiently but stopped when he heard someone approaching from the other side. The door opened and there stood Gen, wearing a black turtleneck and white pants.

“Senku-chan! Hi!”

“'Sup.”

“Come in, come in! I was waiting for you.” He stepped aside to welcome him inside.

He sauntered into the living room and tried to hide that he was kind of impressed. He’d never been in such a spacious apartment before. _He was’t lying, he really is fucking loaded._ "...Nice place."

"Haha, It's usually a mess, I actually cleaned it up just for you!"

_Just for me?_

"Oh, cool.”

Earlier that week his ~~magician~~ _mentalist_ friend had surprised him with an expensive computer part he needed, seemingly out of the blue. Senku sensed that he was fishing for a favor in return, so he took the bait and asked what he wanted in return. Gen told him that he only needed him to come over and model some clothes for him.

_Okay, so some cringy merch. I'll be in and out in no time._

So here he was.

“What was it you said you wanted me to do?"

“Um, I’ll get right to it, because I know how you don’t like to mess around,” laughed Gen. He showed him a white, unlabeled box. “I just want you to try this on. I'll let you go put it on in the spare room, and then you’ll come out and show me. Okay?”

“Sure, whatever.”

“Thanks so much, Senku-chan! I hope you like your surprise,” He chirped.

_Surprise?_

The scientist took the box into the bedroom and shut the door. He sat down on the bed. The box was lighter than he expected; it may as well have been empty. If it did turn out to be empty he would go out there and kick Gen's ass probably. He pursed his lips and opened the lid.

Inside was a yellowish-green tangle of strings and fabric, somewhat neatly folded. 

_What…?_

It sure wasn’t a t-shirt. He selected the first article and held it up. He had to do a double take, but he realized it.

_It's a thong._

It was kind of pathetic. just a string with a little bit of material to cover the front. He wasn't even sure if it would be enough to cover anything at all.

_Seriously?_

He scowled and looked at the door. Outside, Gen was lounging on the couch, waiting for him to come out wearing a fucking thong.

_Oh, fuck off._

He was imagining it already. What, was he supposed to go prance out there and give him a little show? What was he trying to pull? He was already piecing it together but refused to actually say it to himself. Of course Gen was coming onto him. He was always way too flirty and touchy for him for it to be platonic. But, holy shit. Come on.

He set it aside and peered back into the box. He already knew what the second item would be. He picked it up and held it in front of him.

_Yep, it’s a full bikini._

But it wasn't like any swimsuit he'd seen before. like the previous article, it was but a couple of strings with a bit of fabric that was meant to cover his nipples.

He looked in the mirror and held it in front of his chest. He grimaced at how tiny it was. Even with his hoodie on he could tell that it wouldn't leave much to the imagination. It would be more modest to just go without it and be shirtless, in fact.

He was puzzled. _Why did he even bother asking me to wear anything if it's something this_ minimal? _Why not make me go naked?_

He rolled his eyes and set them back down. He disrobed and held the underwear up once more to contemplate his decision.

_Shit, am I really doing this?_

A favor was a favor. He hated owing people, especially someone like Gen. Or that was the half-truth he told himself. If he _really_ hated it he could have thrown it into the trash, stormed out, and demanded Gen change what he wanted to do, or even return his gift. But in his chest was an exhilaration of a sort he’d never felt. _Him,_ Ishigami Senku, the most brilliant man on Earth, wearing a micro bikini and fucking modeling it for someone? What if his peers found out? His heart raced.

_Here goes nothing._

He stepped one leg into the thong, and then the next. He pulled it all the way up. The string nestling itself right into his asscrack felt pretty weird; it was a sensation he hadn't felt before. And he had to walk around like this? The front could barely contain his flaccid cock, and he wasn't even particularly endowed. His balls were almost spilling out of the sides. His mind wandered for a second about what would happen if he were to get hard while wearing it but he quickly shook it off.

He gazed into the mirror. _I'm only halfway done._ He sighed and positioned the micro bikini to preview how it would look on his bare chest. His face heated up from a mixture of embarrassment and arousal when he saw it. It was _way_ too slutty. He'd never in a million years imagine that he'd wear something like this. he gritted his teeth, slipped his arms into the holes, and fidgeted with the strings in the back to tie the knot. He was pretty well-acquainted with knot tying but _damn_ , tying a knot with your hands behind your back while unable to see what you're doing is hard. For a brief moment he considered calling Gen in early to ask for help but _no_ , he wanted to heed his instructions perfectly and be fully "dressed" before emerging.

After a few failed attempts he was able to manage it. And there he was. wearing the sluttiest outfit he could imagine, all courtesy of Gen.

He stared himself down in the mirror. His hardened nipples made a lewd bulge against the thin fabric and don't even get him started on the actual bulge down there.

He felt weird in more ways than one. The longer he looked at himself the more he kinda liked it. His face felt hot and his palms were sweating. He felt his heart racing under the bra.

_Don'tgetharddon'tgetharddon'tgethard._

He gulped and hovered his hand over the knob.

_So… I just… go out there now?_

He gripped the handle. Time seemed to slow to a crawl. _I'm really doing this._ He twisted it and the door creaked open.

His heart was going to beat right out of his chest. He had a fleeting impulse to turn back, close the door, throw his clothes back on and run home, but he didn't.

_It's just trying it on, right? I'll be in and out, right? It's just a favor,_ he justified to himself.

"O-Okay, I'm coming out now…" He did his best to prevent his voice from jumping up an octave from nervousness.

Gen was having no issues. He almost jumped out of his seat when he saw him.

"Senku-chan! You actually did it! Come here, come show me!" He was _elated._

Senku was caught off-guard, but really, what did he actually expect? Of course Gen would be that happy. He always doted on him, after all. What was he thinking?

"…Yeah." He suddenly had a burst of confidence that granted him the will to stay.

"C’mere. Show me everything."

He awkwardly stood before him. He didn't know what to do with his arms. Or his legs. Or his face. Or his anything.

Gen didn't mind at all. “Wooow, so sexy! You're gonna make me cream my pants before we even get started," he laughed.

He didn't know how he was supposed to respond, so he just muttered a _thank you._

_What a bizarre way to come onto someone._

Gen continued. "I'll give you commands and you'll do exactly what I say, okay? I trust that you can be a good boy and follow along."

Senku nodded. Something in Gen's demeanor enticed him into obeying his every command.

He leaned forward, resting his chin on his palm. “Hm… Won’t you strike a pose for me, Senku-chan?”

He stiffly put his arms behind his head and stuck out his hips. Even though he was almost naked the room felt like it was a hundred degrees and he couldn't stop sweating. He pouted a bit and looked to Gen for his reaction.

He softly smiled. “Incredible… it’s like there's an angel standing right before me,” he laughed. "Next time I'll have some heels prepared for you, okay? They'll match the color too, so don't worry! Oh, I'm so excited to see you wear them!"

“Will you really?” His mind was already jumping ahead to what would be in store for other modeling sessions.

“Mhm. I wanna see you wear stockings! And kneesocks! I'll buy you all the clothes in the world and you'll model them all for me! I can't wait!” He directed his gaze down.”Though I won't lie, seeing you in your bare feet is thrilling in its own way…” He’d been rambling non-stop since they started. _He’s so damn noisy,_ Senku thought. Still, the idea of modeling for Gen more kind of made his heart flutter. Something about the constant praise and attention satisfied some need deep inside of him.

Senku glanced down at the bulge straining against Gen's pants. He could feel the droplets of sweat rolling down his body. The room suddenly felt even hotter. _He’s that hard because of me?_ It was weird but he couldn't say he _hated_ it. He felt his cock twitch under his underwear the more he thought about it.

“Can you show me the back now?” Gen asked sweetly.

He turned around. Knowing that Gen was checking out his ass was kind of thrilling. He peeked behind himself and their eyes met for a split second before Senku darted his gaze away. Gen was biting his lip and he was palming his bulge.

_He's gonna masturbate in front of me, isn't he?_

“So good, Senku-chan,” he panted. “Bend over for me and spread your ass?”

He obeyed instinctually as if he made a request as casual as “pass the salt.” The string did basically nothing to hide his asshole and the edges of his little pink hole were in clear view. “T-There you go…” he stammered.

“Oh, wow… I can't help it anymore…” He unzipped his fly and exposed his cock. He stroked it up and down steadily, aided by the precum dribbling down the shaft. "Fuck, you do things to me I can't even describe," he breathed.

Senku's breath hitched. He was right. He was fucking _jacking off_ to him right before his eyes. Unbelievable.

The already tight garment around his hips tightened even more. _Ah, shit._ He was getting hard, too. His erection was going to tent up his underwear in the most humiliating fashion. And Gen was going to watch the whole time. And that idea just made him get harder.

The mentalist was quick to clue in on his arousal, of course. He stopped his hand for a moment. “Oh my, Senku-chan. Is it true that you're getting turned on, too?”

He grimaced. “Maybe…”

“Maybe? You're funny,” he giggled. “Hey, turn around and keep your eyes on me. Look at my cock. I wanna see you all the way hard.” He pulled his pants down a bit to better grasp his dick and began to stroke it again.

The movement of his fist was mesmerizing. In no time he was at full mast, and his penis was embarrassingly straining out of the thong, making the shaft visible from the side.

“Look at you. You love being all pretty, don't you?”

“I-I do.” He cringed to himself after he realized what he’d just answered.

“Hmm… I want more.” He confidently stood up and stepped towards him. Only now did Senku realize how much taller Gen was than him. He tilted his head up to meet his eyes. Gen smiled softly.

“May I touch you, Senku-chan?”

He nodded, awestruck. Gen ran his hands over his torso, admiring every ridge and crevice of his body. “You’re just my type, Senku-chan. You're perfect.”

Senku’s face must have been red as a tomato. He was burning up. He was too stunned to reply.

“You have me weak-kneed…” He smoothly sunk down to the floor as he spoke to kneel before him. Now Gen was the one looking up at him. “I can't help but want to worship you… will you let me, Senku-chan?”

He nodded, and Gen kissed his thigh. “Thank you, darling.” He kissed him up and down, left and right: on his stomach, thighs, hips, circling closer and closer to his goal, so to speak. Senku’s cock strained against the fabric, practically begging to be freed. Gen listened to his silent request and slipped his fingers under the string to pull it down. His dick immediately sprang up, nearly hitting him in the face.

Gen’s hand had found its way back down to his own crotch and he was lazily stroking himself off again. “You're excited too, aren't you, Senku-chan?” He batted his eyes upward and when they met Senku’s it made his heart flutter.

“Yeah,” his voice cracked.

He giggled and kissed the tip, dabbing his lips with precum in the process. “Will you let me please you?”

“Uh-huh.” His voice really did go up an octave now.

“I'm so glad.” He held the shaft in his hand and licked up from the base to the tip just to tease him.Goosebumps ran up and down Senku’s body. He placed his hand on Gen’s head, feeling his silky black hair between his fingers.

Gen licked a couple more times. “You taste incredible, Senku-chan. As good as you look.” He closed his eyes and took the head into his mouth. Senku groaned and gripped his hair. That part was _way_ too sensitive.

“Mm!” He slowly, slowly slipped the rest into his mouth. His warm mouth over his cock felt amazing. He subtly jutted his hips forward to encourage him. Senku was only average-sized, maybe even a little small by some standards, so it didn't take long for Gen’s lips to reach the base. He opened his eyes and looked up, eager to see his companion's expression. He raised an eyebrow as if to ask him how it felt.

_“Feels good… Keep going…”_

The corners of Gen’s eyes crinkled like he was smiling. He closed them again and got back to work. He cutely bobbed his head back and forth and brought up his free hand to fondle his balls, too. Senku’s mind was blurry. It was like nothing he’d felt before; neither hand nor fleshlight could recreate Gen’s mouth. He had trouble holding himself back from thrusting his hips forward to try to facefuck him because he didn't know if that would make him choke. He’d have to ask later if he was okay with that. He instead kept his grip on his hair and guided him while he serviced his cock.

_“Gen…”_ He bent over forwards, overtaken by the pleasure. “I…” He shuddered each time his mouth reached the base and each time he gave his balls a squeeze.

Gen came back up and released him from his mouth. His chin was smeared with saliva and precum. “Are you going to cum soon, my darling Senku-chan?” he asked between gasps for breath.

“I think so…”

He smiled and took it into his mouth. Senku let out a little whine; he was sucking so hard now and he knew it was going to make him burst. Gen worked his tongue all over the shaft while it was inside, and it almost made Senku cum then and there, but at the last moment Gen released him. He looked up at him while he gave the tip a little peck. _“Now_ I'm gonna let you cum.” He opened his mouth wide, stuck out his tongue, and jerked him off fast.

Senku jolted. _“Aaugh!”_ Almost immediately, his thick, white cum splashed onto his tongue. Gen was relentless: he moved his hand faster, eager to milk every last drop out of him. Senku’s whole body tensed up as orgasmic pleasure coursed through him. He could feel Gen’s hot breath on his dick and it drove him wild.

“Oh my fucking— _Gen!”_ More semen splashed on his tongue; he had more inside him than he thought he was capable. Soon it stuttered to a halt as he was finally emptied out.

Gen was jerking off the whole time, and was close to cumming himself. He kept his mouth open to display his handiwork for a second, then closed it and scooted back so Senku could watch him cum.

_“Mmm!”_ He jerked himself off to completion all while holding his load in his mouth. His cum splattered all over the tile floor, making a big mess. He grinned and opened his mouth to show off his prize again, then closed it and gulped it all down in an exaggerated manner.

He slumped back, gasping for breath. His hair was messed up, saliva and semen dribbled down his chin, his cock was out and there was a big puddle of cum on the floor.

Still, he was beaming. “H...How was that, Senku-chan?”

"...Oh my god." Senku collapsed down too and now they were sitting together on the floor like two idiots. The tiles were cold on his bare ass but he didn't give a shit right now. 

Gen crawled towards him and kissed him on the mouth. It tasted salty and now Senku had cum on his face but he kissed him back anyway.

Gen brushed Senku's bangs out of his face. “Next time you model for me I want to fuck you,” he whispered. “Would you like that?”

“Yeah,” he croaked.

Gen staggered to his feet and grabbed Senku’s hand to help him up. “After we clean up I'll make us some tea, ok?” He held his hand as he kissed him again. “Ah, you’re too precious, I just want to shower you in all the love and attention and—”

He cut him off. “T-That’s enough. I’m really gross right now. Tell me later.”

“Ahaha, I see. I'll let you go now.”

Senku turned around. “Can you untie this knot, though?” He gestured to the back of his top.

“Of course.” Gen was skilled with knots too so he had it done in no time.

Senku pulled it off, leaving himself in only the thong. He bunched it up in his fist and ungracefully made his way back to the room in which he changed in earlier. He closed the door and fell onto the bed. He had to hold himself back from screaming into the pillow.

_Holyfuck I had no idea Gen was capable of that._

He took a moment to collect himself and then threw his clothes back on, washed his face, and joined Gen in the kitchen. He grinned to himself as he chatted with Gen like nothing was off, thinking back to his first impressions of their rendezvous.

_Yeah, in and out my ass, I'm gonna be spending a lot of time here._

**Author's Note:**

> an excuse to write a bunch of gen praising and worshiping senku? Maybe.
> 
> [here is the thing i drew for this (obvious nsfw warning).](https://media.discordapp.net/attachments/746359620918050879/777740490824744990/fic_art.png) if you follow my [twitter](https://twitter.com/foggytrees) i have more more bonus art for this scenario and more sengen in general


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